Storing and Retrieving Named Properties in JavaScript Objects

Namaste! Pichhli lesson mein aapne arrays ke through related values ko ordered positions mein store karna seekha: first item index 0, second item index 1, aur so on. Aaj hum us limitation ko solve karenge jahan position se meaning clear nahin hota. For example, agar kisi analysis mein 20 likha hai, to kya woh cloud threshold hai, year hai, ya scale? Object mein value ke saath uska name bhi store hota hai.

Is lesson ke baad aap JavaScript object mein named properties store kar paayenge, unhe dot notation aur bracket notation se retrieve kar paayenge, aur GEE scripts mein readable analysis settings organize karna start kar denge. Yeh automation-oriented GEE workflows ki ek core habit hai.

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Array se object tak: position versus meaning

Array tab useful hai jab order important ho:

const rgbBands = ['B4', 'B3', 'B2'];

print('Red band:', rgbBands[0]);

Yahan rgbBands[0] ka meaning tabhi samajh aata hai jab aapko array ka intended order pata ho.

Lekin analysis settings ke liye named labels better hote hain. Compare kijiye:

const settingsArray = ['Pune', '2023-06-01', '2023-10-31', 20];

Is array mein 20 ka role immediately clear nahin hai. Iske badle object use kijiye:

const analysisSettings = {
  regionName: 'Pune',
  startDate: '2023-06-01',
  endDate: '2023-10-31',
  cloudThreshold: 20
};

Ab har value ke saath uska label hai:

• regionName is 'Pune'
• startDate is '2023-06-01'
• endDate is '2023-10-31'
• cloudThreshold is 20

Object mein har name: value pair ko property kehte hain. Property name ko often key bhi kaha jata hai.

Structure	Value ko kaise identify karte hain?	GIS/GEE example
Array	Index se, such as [0]	Band order, months, class IDs
Object	Named property se, such as .cloudThreshold	Analysis parameters, visualization settings, metadata

Object curly braces {} se banta hai. Har property mein:

1. property name likhiye;
2. colon : lagaiye;
3. value dijiye;
4. next property ho to comma , use kijiye.

const fieldInfo = {
  fieldId: 'F_014',
  cropType: 'Wheat',
  areaHectares: 3.6,
  irrigated: true
};

print('Field information:', fieldInfo);

Object ke properties strings, numbers, booleans, null, arrays, aur even doosre objects bhi hold kar sakte hain. Abhi focus simple, readable configuration objects par rakhenge.

GEE mein aapko visualization objects baar-baar milenge, for example:

const visParams = {
  min: 0,
  max: 3000,
  bands: ['B8', 'B4', 'B3']
};

Yeh script batata hai ki display range kya hai aur red, green, blue channels ke liye kaunse bands use honge. Later modules mein aap ise Map.addLayer() ke saath use karenge.

Important distinction: Aaj ka { ... } ek normal client-side JavaScript object hai. Yeh ee.Dictionary nahin hai. Earth Engine ke server-side objects Module 2 mein aayenge.

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Short video: object ka basic structure

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Properties retrieve karna: dot notation

Object banane ke baad normally humein ek specific setting chahiye hoti hai—not the entire object. Dot notation sabse readable approach hai:

const analysisSettings = {
  regionName: 'Pune',
  startDate: '2023-06-01',
  cloudThreshold: 20
};

print('Region:', analysisSettings.regionName);
print('Start date:', analysisSettings.startDate);
print('Cloud threshold:', analysisSettings.cloudThreshold);

General pattern:

objectName.propertyName

Isko carefully read kijiye:

analysisSettings.cloudThreshold

• analysisSettings poora object hai.
• . ka matlab hai “is object ki property access karo.”
• cloudThreshold exact property name hai.
• Output 20 hoga.

Property names case-sensitive hote hain. Yeh dono different names hain:

const config = {
  cloudThreshold: 20,
  CloudThreshold: 30
};

print(config.cloudThreshold); // 20
print(config.CloudThreshold); // 30

Professional scripts mein ek consistent naming convention bahut useful hoti hai. Multiple words ke property names ke liye camelCase use kijiye:

const projectConfig = {
  studyAreaName: 'Nashik District',
  exportScale: 10,
  targetYear: 2023
};

studyAreaName readable hai aur dot notation ke saath comfortably kaam karta hai.

Avoid kijiye:

// Confusing or inconvenient names:
// 'study area': 'Nashik District'
// cloud-threshold: 20

Space ya hyphen wale property names bracket notation maangte hain. Isliye GEE configuration objects mein camelCase practical default hai.

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Bracket notation: dynamic property names ke liye

Object property retrieve karne ka doosra syntax hai bracket notation:

const analysisSettings = {
  regionName: 'Pune',
  cloudThreshold: 20
};

print('Region:', analysisSettings['regionName']);
print('Cloud threshold:', analysisSettings['cloudThreshold']);

Yeh dot notation ke same value return karta hai:

analysisSettings.regionName
analysisSettings['regionName']

Lekin bracket notation mein property name string ke form mein quotes ke andar likhna hota hai.

Bracket notation tab genuinely useful hota hai jab property name kisi variable mein stored ho:

const analysisSettings = {
  regionName: 'Pune',
  startDate: '2023-06-01',
  cloudThreshold: 20
};

const requestedSetting = 'cloudThreshold';

print('Requested setting:', analysisSettings[requestedSetting]);

Yahan requestedSetting ke andar 'cloudThreshold' hai. JavaScript pehle variable ki value read karta hai, phir us named property ko retrieve karta hai. Output 20 hoga.

Is difference ko yaad rakhiye:

const requestedSetting = 'cloudThreshold';

print(analysisSettings[requestedSetting]);  // 20
print(analysisSettings.requestedSetting);   // undefined

analysisSettings.requestedSetting literal property named requestedSetting ko search karta hai. Woh property object mein hai hi nahin, isliye result undefined hai.

Aapke future reusable scripts mein user-selected parameter, class name, ya selected statistic ko variable ke through choose karne ke cases mein bracket notation kaafi useful hogi.

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Reading: object literal aur access syntax ko consolidate kijiye

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Property update aur new property store karna

Array lesson se ek useful parallel: object ko const se declare karne ke baad bhi uski existing properties update ki ja sakti hain, aur new properties add ki ja sakti hain.

const analysisSettings = {
  regionName: 'Pune',
  cloudThreshold: 20
};

print('Before update:', analysisSettings);

// Existing property update.
analysisSettings.cloudThreshold = 15;

// New property add.
analysisSettings.exportScale = 10;

print('After update:', analysisSettings);
print('Updated threshold:', analysisSettings.cloudThreshold);
print('New export scale:', analysisSettings.exportScale);

Yahan analysisSettings variable same object ko point kar raha hai. Aapne object ko completely replace nahin kiya; sirf uske andar properties change ya add ki hain.

Yeh invalid hoga because const variable ko new object assign kiya ja raha hai:

const analysisSettings = {
  regionName: 'Pune'
};

// analysisSettings = {regionName: 'Mumbai'};

Lekin yeh valid hai:

const analysisSettings = {
  regionName: 'Pune'
};

analysisSettings.regionName = 'Mumbai';

Aap analysis config ke kisi fixed parameter ko code run hone se pehle revise kar rahe hain—this is a normal use case.

Missing property: undefined ko interpret kijiye

Agar aap non-existent property request karte hain, JavaScript generally undefined return karta hai:

const analysisSettings = {
  regionName: 'Pune'
};

print('Cloud threshold:', analysisSettings.cloudThreshold);

undefined ka matlab hai property object mein present nahin hai.

Isko previous lesson ke null se confuse mat kijiye:

const analysisSettings = {
  notes: null
};

print('Notes:', analysisSettings.notes);       // null
print('Owner:', analysisSettings.ownerName);   // undefined

• null means value intentionally empty/set as no value.
• undefined means property was not found or has not been assigned.

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Guided GEE Code Editor practice: readable analysis configuration

Apne current script ki copy save kijiye as:

05_objects_and_properties

Phir yeh script paste karke Run kijiye:

// A named configuration for a future Sentinel-2 analysis.
const analysisConfig = {
  regionName: 'Nashik District',
  startDate: '2023-06-01',
  endDate: '2023-10-31',
  cloudThreshold: 20,
  useCloudMask: true,
  bands: ['B2', 'B3', 'B4', 'B8']
};

// Inspect the complete object.
print('Complete configuration:', analysisConfig);

// Retrieve individual named properties.
print('Study area:', analysisConfig.regionName);
print('Start date:', analysisConfig.startDate);
print('Cloud threshold:', analysisConfig.cloudThreshold);
print('Cloud mask enabled:', analysisConfig.useCloudMask);

// Retrieve with bracket notation.
print('End date:', analysisConfig['endDate']);

// Retrieve a property whose name is held in a variable.
const requestedSetting = 'cloudThreshold';
print('Requested setting:', analysisConfig[requestedSetting]);

// The bands property contains an array.
print('All bands:', analysisConfig.bands);
print('NIR band:', analysisConfig.bands[3]);

// Update an existing property and add a new one.
analysisConfig.cloudThreshold = 15;
analysisConfig.exportScale = 10;

print('Updated configuration:', analysisConfig);
print('Updated cloud threshold:', analysisConfig.cloudThreshold);
print('Export scale:', analysisConfig.exportScale);

Console mein in observations ko verify kijiye:

• Complete configuration expandable object ke form mein show hoga.
• analysisConfig.regionName should show 'Nashik District'.
• analysisConfig['endDate'] should show '2023-10-31'.
• analysisConfig[requestedSetting] should show 20.
• analysisConfig.bands[3] should show 'B8'.
• Update ke baad cloud threshold 15 hona chahiye.
• exportScale initial object mein nahin tha, lekin final printed object mein 10 ke saath appear hoga.

Ab apne script ko career-relevant direction mein personalize kijiye:

1. regionName ko apne kisi familiar district, watershed, forest division, ya city se replace kijiye.
2. startDate aur endDate ko ek meaningful monitoring season ke liye set kijiye.
3. analysisConfig.productName = 'Sentinel-2 SR'; add karke new property inspect kijiye.
4. const requestedSetting = 'exportScale'; karke bracket notation ka output observe kijiye.
5. Intentionally print(analysisConfig.cloudTreshold); likhiye—spelling mein missing h notice kijiye. Output undefined hoga. Phir correct property name restore kijiye.

Yeh last check real GEE debugging habit hai: configuration property ka typo mostly syntax error nahin deta; woh undefined ke through silent problem create kar sakta hai.

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Key takeaways

JavaScript object related information ko named properties ke form mein store karta hai:

const config = {
  cloudThreshold: 20,
  exportScale: 10
};

• Object curly braces {} se banta hai.
• Har property name: value form mein hoti hai.
• Properties comma se separated hoti hain.
• Standard readable access ke liye dot notation use kijiye: config.cloudThreshold.
• Dynamic property names, spaces wale names, ya special property names ke liye bracket notation use hota hai: config['cloudThreshold'].
• config[propertyName] variable ki value use karta hai; config.propertyName literal property named propertyName ko seek karta hai.
• const object ki individual properties update ya add ki ja sakti hain, although poore object ko reassign nahin kar sakte.
• Missing property usually undefined return karti hai.

Next lesson mein hum reusable JavaScript functions likhenge—parameters aur return values ke saath. Objects aapke functions ko clean configuration denge, aur functions repetitive GEE processing steps ko reusable banayenge.